You will get a lot of different ways of doing a brisket, this is just MY personal way of doing them !
Briskets are probably one of if not the most finicky to smoke.... Briskets get done on their own schedule & can get done in as little as 8-10 hrs or can take as long as 12+ hrs. My experience has been the latter....
Now the prep ! Now a lot of folks unpack their brisket and start cutting or trimming off the fat cap.... to each their own but I personally trim up the loose stuff if there is any but do not trim off the fat cap.... I leave it on ! Now the rest of the prep, I rub down with plain yellow mustard, EVOO or peanut oil(I do this with a lot of my smoked meats as it IMHO creates a great barrier to help with keeping in moisture, especially with brisket , pulled pork or beef... Things that are gonna smoke for a while & it gives a great base to apply rub and does not affect the meats turn out, ya can't even taste it....So after rubbing a base, I apply the rub or half the time I just use salt, pepper and a little onion powder and garlic salt.... Then let sit for half hour or so....
Smoker ! I let it heat up to 225*-235* while gettin the prep done, then put er on for a long smokey nap !! LOL. I put the brisket with the fat cap up as IMHO, as it smokes the fat cap so to speak self bastes the brisket...Now around IT of 155*-170 ish, each piece of meats different.... You'll hit what is called the "stall" that can last an hour or sometimes 2+.... This is normal but you'll swear your doing somethin wrong, just decision time here.... Some folks foil to "power thru the stall" & some, myself included crack another cold one & just let it go.... I don't spritz or foil, I just let er go til approx. IT of around 198*, I will start checking for tenderness, i.e. the toothpick test.... Now each brisket is different, I've had some done at 198* IT and some go til 205*+ IT !! The toothpick test means ya just get a good round toothpick and if it slides into the brisket easily, with little resistance, then she's done....
Take out of smoker, wrap in a few layers of foil, couple towels & off to the cooler (I just use my camping cooler) for a few hours for the rest..... The rest will allow the redistribution of the juices into moist, tender & tasty Q !
Again this is just MY way of doing them, there's several methods.... There's no right or wrong way, IMHO..... Ya just gotta experiment & dial in what YOU like !
Hope this helps !